The control of the water content of the blood is an example of homeostasis.

a. Name the part of the body that monitors the water potential of the blood.

In an investigation of the factors that influence urine production, a person drank one litre of water. The person’s urine was collected at half-hourly intervals for four hours after drinking. The results are shown as line A on the figure. On the following day, the same person drank one litre of a dilute salt solution and the urine was collected in the same way (line B). Dilute salt solution has about the same water potential as blood plasma.

b. Calculate how much urine was produced in the two hours after drinking the litre of water.

c. Explain why the person produced so much urine after drinking the litre of water.

d. Suggest why the results during the second day were so different from those on the first day.

e. Explain why negative feedback, and not positive feedback, is involved in homeostatic mechanisms.

Transcribed Image Text:

500 400 300 200 100 - B. *- - * 4 Time/h time of drinking Urine output/cm' per 30 min A.